Gas turbine combustors have used axially staged fuel injection to reduce NOx (nitrogen oxides) and CO (carbon monoxide) emissions. NOx emissions increase with combustion temperature and residence time. For this reason, Dry Low NOx (DLN) combustors premix fuel and air to reduce peak combustion temperature. However, CO emissions increase as the combustion becomes cooler or residence time is reduced. This means that, in general, reducing CO emissions results in an increase in NOx and vice versa, making it difficult to reduce both forms of emissions simultaneously. It has been found beneficial to reduce airflow to the primary combustion zone during low-load operation to simultaneously maintain acceptable emissions of both CO and NOx. Prior methods for reducing this airflow include variable inlet vanes on the compressor that control total airflow, and compressor bleeds that divert air around the combustion system.